当我使用类中定义的函数时，它们不会被识别为已定义

问：

我有这段代码，但是当我尝试使用重新定义的 str 函数时，它不会打印任何内容，更重要的是，名为“cuadrant”的定义函数不起作用，因为它不是根据 python 定义的，但它是：

class Point:
    def __init__(self, x = 0, y = 0):
        self.x = x
        self.y = y
        print('The point ({},{}) has been created'.format(self.x, self.y))

    def __del__(self):
        print('The point ({},{}) has been deleted or overwritten'.format(self.x, self.y))

    def __str__(self):
        return '({},{})'.format(self.x, self.y)

    def cuadrant(self):
        if self.x > 0 and self.y > 0:
            return '1st Cuadrant'
        elif self.x < 0 and self.y > 0:
            return '2nd Cuadrant'
        elif self.x < 0 and self.y < 0:
            return '3rd Cuadrant'
        elif self.x >0 and self.y < 0:
            return '4th Cuadrant'
        else:
            return 'Original Point'

A = Point(4, 5)
B = Point(8, 9)

str(A)
str(B)

cuadrant(A)
cuadrant(B)

我得到的错误消息是这样的：

runfile('C:/Users/Jorge87/Desktop/Master Tema 1.5/prueba.py', wdir='C:/Users/Jorge87/Desktop/Master 
Tema 1.5')
The point (4,5) has been created
The point (8,9) has been created
Traceback (most recent call last):

File "<ipython-input-9-16e5df591861>", line 1, in <module>
runfile('C:/Users/Jorge87/Desktop/Master Tema 1.5/prueba.py', wdir='C:/Users/Jorge87/Desktop/Master 
Tema 1.5')

File "C:\ProgramData\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 
827, in runfile
execfile(filename, namespace)

File "C:\ProgramData\Anaconda3\lib\site-packages\spyder_kernels\customize\spydercustomize.py", line 
110, in execfile
exec(compile(f.read(), filename, 'exec'), namespace)

File "C:/Users/Jorge87/Desktop/Master Tema 1.5/prueba.py", line 38, in <module>
cuadrant(A)

NameError: name 'cuadrant' is not defined